This invention relates to methods of manufacturing semiconductor integrated circuit (IC) devices and to lead frames used in such manufacturing methods and, more particularly, is directed to a method of manufacturing a semiconductor IC device, such as a monolithic IC, a hybrid IC or the like, and to a lead frame used in such a manufacturing method.
In semiconductor integrated circuit devices in which a control portion and a power portion having a power element associated with the control portion are fabricated on a single semiconductor chip, it is known that the heat generated by the power portion affects the electrical characteristics of the control portion, interfering with the control relationship between the control portion and the power portion.
FIG. 3 shows a conventional IC die structure arranged to solve that problem. In FIG. 3, a semiconductor chip Ta having a control portion and a separate semiconductor chip Tb including a power portion are mounted in spaced relation on a die pad D of a lead frame. As a result, heat generated by the power portion Tb is not conducted directly to the control portion Ta but is conducted to the control portion Ta only indirectly through the die pad D. Since the semiconductor chip Ta and the semiconductor chip Tb are thus separated from each other and the heat generated by the power portion Tb is not conducted directly to the control portion Ta as described above, the control portion Ta is not affected by the heat generated in the power portion Tb.
In this arrangement, however, die bonding has to be carried out separately for each of the chips Ta and Tb. Consequently, if a semiconductor IC device is made with a plurality of semiconductor chips, for example, two semiconductor chips as in the conventional example of FIG. 3, then the die bonding step has to be carried out as many times for each die pad as the number of the semiconductor chips mounted on the die pad, i.e., twice as in the conventional example of FIG. 3. Therefore, the time required for die bonding is increased and the cost of die bonding is increased correspondingly.